Subject: Re: UVM/other problems for desktop users in current?
To: Ross Patterson <Ross.Patterson@CatchFS.Com>
From: Manuel Bouyer <email@example.com>
Date: 12/23/2002 18:18:53
On Thu, Dec 19, 2002 at 04:43:09PM -0500, Ross Patterson wrote:
> On Thursday 19 December 2002 01:03 pm, Dan Melomedman wrote:
> > Ross Patterson wrote:
> > > To sum up, has it been definitively established that softdeps are safe?
> > The way I understand it is they were designed to guarantee metadata
> > integrity, not data integrity.
> If I read McKusick & Ganger's papers correctly, softdeps were designed to
> provide the same degree of metadata integrity as synchronous writes with the
> improved runtime performance of asynchronous writes and the improved
> dirty-mount performance of journaled filesystems. The sacrifice was to
> accept the lower degree of file-data integrity that asynchronous writes
> So if softdeps are working correctly, you gain performance but you lose some
> file-data integrity on open files that haven't been fsync()'ed. That's a
Even with traditional BSD ffs mounted with default options you don't have
guarantees on file-data integrity. Only synchronous mount can give you that.
Manuel Bouyer <firstname.lastname@example.org>
NetBSD: 23 ans d'experience feront toujours la difference